Application of group V polyoxometalate as an efficient base catalyst: a case study of decaniobate clusters†
The base catalytic activity of the decaniobate cluster (TMA)6[Nb10O28]·6H2O (TMA+ = tetramethylammonium cation) was studied theoretically and experimentally. Density functional theory calculations showed that the oxygen atoms in the cluster are highly negatively charged and suggested the possibility that the cluster can act as a base catalyst. We demonstrated for the first time that [Nb10O28]6− actually exhibits base catalytic activity for aldol-type condensation reactions including Knoevenagel and Claisen–Schmidt condensation reactions. The catalytic reactions proceeded under ambient conditions, suggesting that [Nb10O28]6− holds promise as a practical strong base catalyst.